The objective of the proposed work is to identify some immunological mechanisms responsible for glomerulo- and tubulointerstitial nephritis in experimental animals and in man. The possibility that the same immunological mechanisms inducing renal injury may have a role in the pathogenesis of inflammatory lesions in the lung, in the intestine, and in the serosae will also be studied. Attempts will be performed to identify the antigens responsible for the systemic autoimmune disease induced in animals by exposure to mercuric chloride, a common agent of pollution. The permeability of the gastrointestinal tract of rabbits with immune complex gastrointestinal disease will be investigated in order to establish an experimental model of "protein-loosing enteropathy". Lastly, the cytotoxic effect of antibody to tubular brush border will be examined with special focus on antibody-mediated functional alterations of the proximal convoluted tubules.